Archive for February, 2012

Hacking the Klipsch ProMedia GMX D-5.1

February 11, 2012

I saw a Klipsch ProMedia GMX D5.1 at a friend’s house about 8 years ago.  This is an amplifier/speaker system with a large bass speaker and five smaller midrange/treble speakers with a somewhat “spaceage” look.  Most of the “brains” of the system reside in a small saucer-shaped pod which you use for audio connections and mode, tone, and volume controls. The amplifiers for the speakers are in the bass box, and the connections are on the back of that box.  The system looks like this:

Since I was about to move into a new house, I purchased 3 of the systems, knowing that I had places picked out for 2, with the remaining one in reserve. Within a few years, one of the control pods died; a year later, another died. The prices that Klipsch wanted for repair were ridiculous.

I searched the web and found a number of pages that claimed to reveal the circuitry of these devices, but none of the pictures matched my units.  It turned out that while Klpisch made some fairly complex systems at one point, where the signal processing was done inside the bass box, my system was much simpler.  There is a single DIN connector with 7 signal wires plus a ground.  The signal processing of the audio signals is done in the pod, but the amplifiers for all 6 speakers are inside the bass enclosure, and they were still working fine.  All I needed to do was supply appropriate signals to the connector, and I could still use it as an amplifier/speaker system, albeit without the convenience or “smarts” of the original brain/pod. This is what the back of my bass box looks like:

I determined that the wires coming from the DIN connecter were used follows:

  • White – bass
  • Red – front right
  • Blue – front left
  • Green – surround right
  • Orange – surround left
  • Black – center
  • Yellow – not used

My immediate need was for a very simple system, a monaural amplifier for my electronic drum kit.  I purchased five “hanger screws” that have wood threads on one end and machine threads on the other.  You drill a hole in wood, screw the wood-thread side into the wood, and then have a machine thread available poking out of the wood.  I determined the thread used to mount the speakers (1/4-20), inserted the hanger screws in the top of the bass enclosure, and mounted the speakers there.

This shows the first hanger screw after I screwed it into the bass box:

And this shows the first speaker mounted to the box:

And this shows the final system, which is working very nicely as a practice amplifier/speaker for my electronic drums: